Researchers don't have enough high-tech monitoring stations to track every instance of ground shaking, so they're enlisting help from ordinary people to document quakes and pinpoint areas of possible damage.

Almost anyone can participate by equipping laptop computers with special software or installing quake sensors at home.

“If they can provide scientific data that can prepare us for events in the future, then that's extremely important,” said Tom Jordan of the Southern California Earthquake Center at the University of Southern California.

The epicenter of the movement is in California, the most quake-prone state in the continental United States. Each year, about 10,000 temblors rattle Southern California alone, though most are too small to be felt.

The Quake-Catcher Network was launched this year to tap into the computing power of about 300 participants worldwide, including 50 volunteers in California.

The network relies on a sensor called an accelerometer that is built into many newer laptops to detect sudden motion. If the computer is dropped, for instance, the sensor alerts the hard drive, shielding it from damage and preventing data from being lost.

Volunteers download software that links their computers to others in the network and sends information about shaking to scientists through the Internet.

Since any movement – passing trucks, neighbors moving furniture or a pet jumping on the desk – can trigger a laptop's internal sensor, scientists scan incoming data only when the U.S. Geological Survey determines a quake has occurred, based on readings from its field stations.

The computer network, run by Stanford University and the University of California Riverside, supplements data from about 800 permanent monitoring stations in California that beam readings to the USGS, the federal agency in charge of monitoring for quakes.

Emergency personnel use the data to locate potentially hard-hit areas. The more sensors that can record shaking, the more accurate the picture about possible damage.

The volunteer system is similar to one used by the Search for Extraterrestrial Intelligence project at the University of California Berkeley. Started in 1999, the SETI system harnesses shared PC power to analyze radio-telescope data for sounds of alien intelligence. It boasts more than 1 million volunteers.

The Quake-Catcher system was put to the test in July during a magnitude-5.4 quake that was centered in the hills east of Los Angeles. The temblor rattled a large swath of Southern California but caused little damage. Fewer than a half-dozen laptops with the software sensed the quake, and only three sent back clean signals seven seconds after the fault ruptured.

While scientists were pleased some laptops detected motion, they acknowledged the system needed work.

Seismology graduate student Julian Lozos of UC Riverside was among those whose laptop sent back good data. Since installing the program last winter, he has kept it running, except when he sleeps, and has not noticed any slowing of his computer's performance.

The project, initially limited to Apple computer users, was expanded this summer to include Lenovo Thinkpads. Scientists are developing software compatible with other PCs.